Sunflower in Zone 5A — Great Plains

Sunflowers are a classic for a reason. Their cheerful faces brighten any garden, and the seeds are a tasty treat, whether you're snacking on them yourself or leaving them for the birds come winter. Plus, they're surprisingly versatile in the kitchen and make stunning cut flowers that can handle our intense Plains sunshine.

Growing sunflowers here on the Plains does come with some challenges. We have to deal with extreme temperature swings, occasional hail, and periods of drought. But with a little planning and attention to timing within our roughly 168-day growing season, you can definitely enjoy these beauties in your own backyard.

Starting sunflower seeds indoors is an option, but direct sowing is generally preferred. It really only makes sense if you're aiming for an extra-early bloom or want a head start on the season, especially further north in our region where the growing season is shorter. If you do start indoors, do it in early to late April, about three weeks before you plan to transplant.

Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist, watering from the bottom to avoid damping off, and provide plenty of warmth and light. Be mindful that our spring weather can be variable, so keep an eye on the forecast and adjust your indoor environment as needed.

Transplant your sunflower seedlings outdoors in early to late May, once the risk of frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature fluctuations common in the Plains.

When transplanting, space the seedlings 18-24 inches apart. Choose a sunny spot with well-drained soil, and be prepared to protect them from strong winds, which can easily damage young plants. Keep an eye on the forecast for late frosts, and be ready to cover your seedlings if needed.

Direct sowing is the easiest and most common way to grow sunflowers here on the Plains. Wait until late April through early July to sow your seeds directly into the garden. The soil should be warm, ideally around 60°F, for best germination.

Prepare the soil by loosening it and adding some compost or other organic matter. Plant the seeds about 1 inch deep and space them 18-24 inches apart. Keep the soil consistently moist until the seedlings emerge. Sunflowers are easy to grow and grow quickly in our prairie soil!

Sunflowers are moderately drought-tolerant once established, thanks to their deep taproots, which is a big plus in our region. However, consistent watering is important, especially during the initial growth stages and during extended dry periods. Our rainfall can be variable, so don't rely solely on Mother Nature.

During the hot summer months, especially when temperatures are hitting those typical highs of 93°F, water deeply about once a week, providing about 1 inch of water. Use the finger test: if the top 2 inches of soil feel dry, it's time to water. Water at the base of the plant to avoid wetting the foliage, especially with our low-to-moderate humidity.

Keep an eye out for signs of underwatering, such as wilting leaves, or overwatering, such as yellowing leaves. A good layer of mulch around the base of the plants can help retain moisture and suppress weeds, which is helpful during our hot summers.

In our region, you can expect your first sunflower harvest from mid-July through early October, depending on when you planted. For sunflower seeds, wait until the back of the flower head turns brown and the seeds are plump and slightly loose.

To harvest the seeds, cut the entire flower head off the stalk, leaving about a foot of stem. You can then hang the head upside down in a dry, well-ventilated place to dry completely. For cut flowers, harvest them when the petals first open, and place them in water immediately.

As our first frost approaches in early October, harvest any remaining flower heads, even if they're not fully mature. You can still dry the seeds indoors or enjoy the cut flowers.

Here are three common problems you might encounter growing sunflowers on the Great Plains:

Birds Eating Seeds

• What it looks like: Sunflower heads with missing seeds or signs of pecking.
• What causes it: Birds, especially finches and sparrows, love sunflower seeds. This is especially prevalent as the seeds ripen, and other food sources become scarce.
• How to fix/prevent it: Cover the developing flower heads with netting or mesh bags. You can also try planting extra sunflowers specifically for the birds.

Sunflower Moth

• What it looks like: Small caterpillars inside the sunflower head, feeding on the seeds. You might also see webbing and frass (caterpillar droppings).
• What causes it: Sunflower moths lay their eggs on the developing flower heads. The larvae hatch and burrow into the head to feed.
• How to fix/prevent it: Inspect flower heads regularly for signs of infestation. Remove and destroy any infested heads. You can also use Bacillus thuringiensis (Bt), a biological insecticide, to control the larvae.

Downy Mildew

• What it looks like: Yellow patches on leaf tops with fuzzy gray-purple growth on undersides. Leaves brown and die from the bottom up.
• What causes it: An oomycete pathogen that spreads in cool, humid conditions via wind-carried spores.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation. Water at the base, never overhead. Copper-based fungicides for prevention. Plant resistant varieties where available.

Great Plains Specific Challenges: Our hot summers and variable rainfall can stress sunflowers, making them more susceptible to pests and diseases. Consistent watering during dry spells and good air circulation can help prevent problems. The strong winds we often experience can also damage tall sunflowers, so provide support if needed.

Sunflowers make great companions for a variety of plants. Cucumbers and squash benefit from the shade provided by sunflowers, which helps to keep the soil cool and moist. Green beans can use the sunflower stalks as a natural trellis. Corn and sunflowers are classic companions, as they both thrive in full sun and have similar nutrient requirements. Lettuce can benefit from the partial shade provided by sunflowers, especially during the hottest part of the summer.

Avoid planting potatoes near sunflowers, as they compete for the same nutrients in the soil. Potatoes are also susceptible to some of the same diseases as sunflowers, which can increase the risk of infection.